How to limit cook loss when preparing cod (Gadus morhua): The constraints of temperature and time

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On the use of pulsed electric field technology as a pretreatment to reduce the content of potentially toxic elements in dried Saccharina latissima

Seaweeds, like sugar kelp, are increasingly popular for food production, but their application is often limited by the content of iodine and other potentially toxic elements (PTEs). Boiling and blanching are efficient in reducing the iodine content (-38-94%), but are energy demanding processes and could therefore be too expensive for viable commercial applications. Pulsed electric field (PEF) processing is gaining interest for commercial processing of seaweeds, aiming to reduce the energy demand for the pre-treatment. In this work, two conditional settings (energy levels: 2.7 and 14.4 kJ/kg) of PEF were evaluated as pretreatments prior to drying of sugar kelp, and compared to no pretreatment and freezing/thawing at −20/4 °C. Both PEF treatments reduced the iodine content significantly, by approximately 40%, compared to no pretreatment. Similarly, the content of mercury was reduced by approximately 19%. Freezing prior to drying did not significantly alter the content of PTEs in dried kelp. The energy input associated with PEF processing was <10% of the calculated input for traditional processing. These findings are promising as the industry is looking into rapid, non-destructive processing methods for reducing the energy requirements associated with drying and preservation, while improving the safety of products.publishedVersio

Thaw rigor in Atlantic salmon (Salmo salar) fillets, as affected by thawing rate and frozen storage time

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Effects of capture-related stress and pre-freezing holding in refrigerated sea water (RSW) on the muscle quality and storage stability of Atlantic mackerel (Scomber scombrus) during subsequent frozen storage

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Predicting liquid loss of frozen and thawed cod from hyperspectral imaging

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Food Microstructure and Fat Content Affect Growth Morphology, Growth Kinetics, and Preferred Phase for Cell Growth of Listeria monocytogenes in Fish-Based Model Systems

Food microstructure significantly affects microbial growth dynamics, but knowledge concerning the exact influencing mechanisms at a microscopic scale is limited. The food microstructural influence on Listeria monocytogenes (green fluorescent protein strain) growth at 10°C in fish-based food model systems was investigated by confocal laser scanning microscopy. The model systems had different microstructures, i.e., liquid, xanthan (high-viscosity liquid), aqueous gel, and emulsion and gelled emulsion systems varying in fat content. Bacteria grew as single cells, small aggregates, and microcolonies of different sizes (based on colony radii [size I, 1.5 to 5.0 μm; size II, 5.0 to 10.0 μm; size III, 10.0 to 15.0 μm; and size IV, ≥15 μm]). In the liquid, small aggregates and size I microcolonies were predominantly present, while size II and III microcolonies were predominant in the xanthan and aqueous gel. Cells in the emulsions and gelled emulsions grew in the aqueous phase and on the fat-water interface. A microbial adhesion to solvent assay demonstrated limited bacterial nonpolar solvent affinities, implying that this behavior was probably not caused by cell surface hydrophobicity. In systems containing 1 and 5% fat, the largest cell volume was mainly represented by size I and II microcolonies, while at 10 and 20% fat a few size IV microcolonies comprised nearly the total cell volume. Microscopic results (concerning, e.g., growth morphology, microcolony size, intercolony distances, and the preferred phase for growth) were related to previously obtained macroscopic growth dynamics in the model systems for an L. monocytogenes strain cocktail, leading to more substantiated explanations for the influence of food microstructural aspects on lag phase duration and growth rate. IMPORTANCE Listeria monocytogenes is one of the most hazardous foodborne pathogens due to the high fatality rate of the disease (i.e., listeriosis). In this study, the growth behavior of L. monocytogenes was investigated at a microscopic scale in food model systems that mimic processed fish products (e.g., fish paté and fish soup), and the results were related to macroscopic growth parameters. Many studies have previously focused on the food microstructural influence on microbial growth. The novelty of this work lies in (i) the microscopic investigation of products with a complex composition and/or structure using confocal laser scanning microscopy and (ii) the direct link to the macroscopic level. Growth behavior (i.e., concerning bacterial growth morphology and preferred phase for growth) was more complex than assumed in common macroscopic studies. Consequently, the effectiveness of industrial antimicrobial food preservation technologies (e.g., thermal processing) might be overestimated for certain products, which may have critical food safety implications.acceptedVersio

Effect of food microstructure on growth dynamics of Listeria monocytogenes in fish-based model systems

Traditionally, predictive growth models for food pathogens are developed based on experiments in broth media, resulting in models which do not incorporate the influence of food microstructure. The use of model systems with various microstructures is a promising concept to get more insight into the influence of food microstructure on microbial dynamics. By means of minimal variation of compositional and physicochemical factors, these model systems can be used to study the isolated effect of certain microstructural aspects on microbial growth, survival and inactivation. In this study, the isolated effect on microbial growth dynamics of Listeria monocytogenes of two food microstructural aspects and one aspect influenced by food microstructure were investigated, i.e., the nature of the food matrix, the presence of fat droplets, and microorganism growth morphology, respectively. To this extent, fish-based model systems with various microstructures were used, i.e., a liquid, a second more viscous liquid system containing xanthan gum, an emulsion, an aqueous gel, and a gelled emulsion. Growth experiments were conducted at 4 and 10 °C, both using homogeneous and surface inoculation (only for the gelled systems). Results regarding the influence of the growth morphology indicated that the lag phase of planktonic cells in the liquid system was similar to the lag phase of submerged colonies in the xanthan system. The lag phase of submerged colonies in each gelled system was considerably longer than the lag phase of surface colonies on these respective systems. The maximum specific growth rate of planktonic cells in the liquid system was significantly lower than for submerged colonies in the xanthan system at 10 °C, while no significant differences were observed at 4 °C. The maximum cell density was higher for submerged colonies than for surface colonies. The nature of the food matrix only exerted an influence on the maximum specific growth rate, which was significantly higher in the viscous systems than in the gelled systems. The presence of a small amount of fat droplets improved the growth of L. monocytogenes at 4 °C, resulting in a shorter lag phase and a higher maximum specific growth rate. The obtained results could be useful in the determination of a set of suitable microstructural parameters for future predictive models that incorporate the influence of food microstructure on microbial dynamics

Isolating the effect of fat content on Listeria monocytogenes growth dynamics in fish-based emulsion and gelled emulsion systems

The influence of food matrix fat content on growth kinetics of bacteria is quite complex and, thus far, not fully elucidated, with different studies reporting contradictory results. Since results in studies involving real food products are possibly influenced by variations in compositional and physicochemical properties, there is a need for systematic studies in artificial food model systems among which the influence of fat content is effectively isolated. In this study, the isolated effect of a gradual increase in fat content, in the range of 1–20% (w/w), on the growth dynamics of Listeria monocytogenes in fish-based emulsion and gelled emulsion model systems was investigated at 4, 7 and 10 °C. Growth parameters estimated by the Baranyi and Roberts model were compared among the different model systems. Overall, an increase from 1 to 5% fat resulted in a significant reduction of the lag phase duration λ in both model systems at all studied temperatures, while a further increase in fat content did not significantly affect λ. The relationship between the fat content (%) and the maximum specific growth rate μmax was more complex, following the same trends for both emulsions and gelled emulsions and tested temperatures, i.e., (i) μmax was higher at 5% than at 1% fat, (ii) μmax was lower at 10% than at 5% fat, (iii) μmax at 20% fat was higher than or equal to μmax at 10% fat, and (iv) μmax was the highest at 5% fat. Based on these experiments, fundamental knowledge was provided which could lead to the development of food matrix-related factors describing the influence of fat content in future predictive modeling tools which include food microstructural elements. Such models could increase the accuracy of the shelf-life estimation for fat-containing foods, in turn resulting in improved food safety